title: Electrospinning as a new technique to control the crystal morphology and molecular orientation of polyoxymethylene nanofibers.
abstract: Electrospinning is widely accepted as a simple and versatile technique for producing nanofibers. The present work, however, introduces a new concept of the electrospinning method for controlling the crystal morphology and molecular orientation of the nanofibers through an illustration of a case study of polyoxymethylene (POM) nanofibers. Isotropic and anisotropic electrospun POM nanofibers are successfully prepared by using a stationary collector and a rotating disk collector. By controlling the voltage and the take-up velocity of the disk rotator, the morphology changes between an extended chain crystal (ECC) and a folded chain crystal (FCC) as clarified by a detailed analysis of the X-ray diffraction and polarized infrared spectra of the POM nanofibers. Herman's orientation function and dichroic ratio lead us to a schematic conclusion--that (i) molecular orientation is parallel to the fiber axis in both isotropic and anisotropic POM nanofibers, (ii) a single nanofiber consists of a nanofibril assembly with a size of 60-70 A and tilting at a certain degree, and (iii) the higher the take-up velocity, the smaller the nanofibril under the (9/5) helical structure of the POM chains. It should be emphasized here that the electrospinning method is no longer a single nanofiber producer but that it can be applied as a new instrument to control the morphology and chain orientation characteristics of polymer materials, opening a new research field in polymer science where we can understand the relationship between structure at the molecular level and the properties and performance at the macroscopic level.
authors.affiliation: The Petroleum and Petrochemical College, Chulalongkorn University, Chula Soi 12, Phyathai Road, Pathumwan, Bangkok, Thailand 10330.
authors.forename: Thontree
authors.initials: T
authors.lastname: Kongkhlang
authors.forename: Kohji
authors.initials: K
authors.lastname: Tashiro
authors.forename: Masaya
authors.initials: M
authors.lastname: Kotaki
authors.forename: Suwabun
authors.initials: S
authors.lastname: Chirachanchai
mesh_terms: D003460:Crystallization; D004583:Electrons; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D012117:Resins, Synthetic / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D012117:Resins, Synthetic; C010102:delrin